Verifying the presence of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy

This paper examines the problems associated with analysis of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy (EELS) on the transmission electron microscope (TEM). The detection of neptunium in a matrix of uranium can be impeded by the occurrence of a plural scattering event from uranium (U-M5 + U-O4,5) that results in severe overlap on the Np-M5 edge at 3665 eV. Low levels of Np (1600-6300 ppm) can be detected in a uranium solid, uranophane [Ca(UO2)2(SiO3OH)2(H2O)5], by confirming that the energy gap between the Np-M5 and Np-M4 edges is at 184 eV and showing that the M4/M5 ratio for the neptunium is smaller than that for uranium. The Richardson-Lucy deconvolution method was applied to energy-loss spectral images and was shown to increase the signal to noise ratio.